1. If it is used as noun:
Your mother is the woman who gave birth to you. You can also call someone your mother if she brings you up as if she was this woman. You can call your mother 'Mother'.
2. If it is used as verb:
If a woman mothers a child, she looks after it and brings it up, usually because she is its mother.
If you mother someone, you treat them with great care and affection, as if they were a small child.